1// Copyright (c) 2011 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "base/test/test_file_util.h"
6
7#include <sys/mman.h>
8#include <errno.h>
9
10#include "base/logging.h"
11#include "base/file_util.h"
12#include "base/files/memory_mapped_file.h"
13
14namespace file_util {
15
16bool EvictFileFromSystemCache(const base::FilePath& file) {
17  // There aren't any really direct ways to purge a file from the UBC.  From
18  // talking with Amit Singh, the safest is to mmap the file with MAP_FILE (the
19  // default) + MAP_SHARED, then do an msync to invalidate the memory.  The next
20  // open should then have to load the file from disk.
21
22  int64 length;
23  if (!base::GetFileSize(file, &length)) {
24    DLOG(ERROR) << "failed to get size of " << file.value();
25    return false;
26  }
27
28  // When a file is empty, we do not need to evict it from cache.
29  // In fact, an attempt to map it to memory will result in error.
30  if (length == 0) {
31    DLOG(WARNING) << "file size is zero, will not attempt to map to memory";
32    return true;
33  }
34
35  base::MemoryMappedFile mapped_file;
36  if (!mapped_file.Initialize(file)) {
37    DLOG(WARNING) << "failed to memory map " << file.value();
38    return false;
39  }
40
41  if (msync(const_cast<uint8*>(mapped_file.data()), mapped_file.length(),
42            MS_INVALIDATE) != 0) {
43    DLOG(WARNING) << "failed to invalidate memory map of " << file.value()
44                  << ", errno: " << errno;
45    return false;
46  }
47
48  return true;
49}
50
51}  // namespace file_util
52